Gamma rays reveal an intermediate black hole

Schwarzes Loch

Intermediate black holes have so far been considered a “missing link”, as so far only a few candidates for medium-sized black holes have been discovered. Now a team of astronomers has tracked another sample of this intermediate phase between stellar and supermassive black holes. This was successful because the object acted as a gravitational lens and its mass distorted the radiation of the gamma rays in a far-reaching way. According to this, the mass of this object is 55,000 solar masses and therefore it can neither be formed in a simple star explosion, nor can it sit as a super massive gravitational giant in the center of the galaxy.

Almost all black holes discovered so far by astronomers fall into two categories. Either they are maximum black holes with a mass of about 50 solar masses, such as in a massive star supernova. Or they are giant giants with one million to ten billion solar masses that sit in the center of galaxies. The mass at the middle, however, is an interval, although by principle there must also be an intermediate black hole. These can occur as a result of multiple mergers of stellar black holes, as they most likely occur in the middle of spherical clusters, or by massive mergers of stars with a mass of about 1000 solar masses in the megastar, which is then a black hole Fall into However, so far, there are only few candidates for such “missing links” in black hole populations.

Tell-story echo in gamma-ray pulse

Astronomers now working with James Pennanter at the University of Melbourne may have tracked another candidate for an intermediate black hole in a new way. For their study, the team evaluated subtle delays in light from distant gamma-ray bursts. Star supernovae or collisions have, among other things, these small but extremely strong rays. A portion of the energy released in the process moves out into space in the form of short-wave, very high-energy gamma-rays, which can still be detected with a gamma-ray telescope orbiting the Earth from a distance of millions . Billions of light years. When these gamma rays cross an object along the path of the Earth with a large, compact mass, for example a galaxy, a star cluster or a large black hole, its gravitational effect slightly deflects radiation.

This leads to a gravitational lens effect: with visible light, the distortion of light due to gravity can result in enlarged double images or rings of light; It is similar to gamma rays. But because gamma ray telescopes do not have sufficiently high spatial resolution, such gravity shows the lens effect as a characteristic splitting and delaying of the signal: “The observational signature of such a lens phenomenon is the initial gamma ray pulse. A Explain ‘resonance’, Paynter and his team. Exciting thing about it: From the delay and characteristics of this resonance, it is possible to read the mass and properties of the cosmic object that deflected the gamma radiation. So the researchers for an echo signal Discovered a data set of 2,700 gamma-ray bursts, which have the characteristics of an intermediate black hole.

Lens flare matches intermediate black hole

Astronomers found what they were looking for in a gamma ray burst: the short burst GRB 950830 showed a radiation curve, indicating the effect of a gravitational lens with about 55,000 solar masses. “There are three celestial bodies in this mass range that can serve as lenses: the manifestation of spherical clumps, dark matter, or black holes,” write Paynter and his colleagues. According to your calculations, the spherical clusters are very few and do not match the internal distribution of their mass to the observed distortion of gamma rays. In the opinion of astronomers, there is much to suggest that there is a black hole behind this gravitational lens effect during gamma-ray bursts. And due to its mass, it would have to be one of the long-sought intermediate black holes.

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Also exciting: “This newly discovered black hole may be an old relic – a primary black hole formed in the early universe by the first stars and galaxies,” explains Monash University co-author Eric Thran. “These early black holes may be the nucleus of the supermassive black holes that lie in the midst of galaxies today.” However, astronomers believe that they are formed by the merger of smaller precursors and further growth. “We know that these supermassive black holes are in the largest, if not all, galaxies. But we still cannot understand how these giants can be so big from the beginning of the universe.

Quail: Nature Astronomy, doi: 10.1038 / s41550-021-01307-1

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